Heat exchange systems, such as are associated with internal combustion engines, typically employ as a heat transfer medium an aqueous alcohol solution having one or more additives capable of protecting metal components in contact with same from corrosive attack.
Owing to the increasing use of aluminum in engine cooling systems it is essential that the heat transfer fluids employed therein adequately inhibit corrosive attack on this material. It is particularly desirable that such fluids protect aluminum against the type of corrosion known as "cavitation erosion corrosion" (C/E/C) which occurs at heat rejecting surfaces of a system such as the exhaust port areas of cylinder heads. The products of aluminum cavitation erosion corrosion ultimately form deposits, the accumulation of which can significantly impair a coolant system's heat transfer ability. Not infrequently, an additive's ability to inhibit aluminum corrosion under more moderate conditions will not be determinative of its ability to provide protection in the high temperature environment associated with C/E/C.
The use of silicon-containing additives as corrosion inhibitors in alcohol based compositions, such as antifreezes, is well known in the art. For example, U.S. Pat. No. 3,234,144, to Morehouse et al., discloses the use of organo-functional compounds including hydrocarbonoxysilanes and siloxanes as corrosion inhibitors in antifreeze compositions. Similarly, U.S. Pat. Nos. 3,337,496 and 3,341,469, both to Pines et al., disclose the use of copolymers of at least one siloxane group and at least one silicate group as additives to inhibit the corrosion of metals in contact with aqueous liquids. As a further illustration, U.S. Pat. No. 4,514,315, to Matulewicz et al., discloses the use of an alkylene silane grafted polyether, comprising the reaction product of an unsaturated grafting silane and a base polyether, as an aluminum corrosion inhibiting additive in aqueous or alcohol solutions.
Notwithstanding the prior art's disclosure of the utility of silicon-containing compounds as corrosion inhibitors, it is well known that not all silicon-containing compounds will afford protection against aluminum corrosion. In fact, many silanes have a tendency to promote aluminum corrosion, particularly under high temperature conditions. U.S. Pat. No. 4,514,315 discloses that under conditions of nucleate boiling, a polyalkylene oxide polymer grafted with vinyltrimethoxysilane provided an aqueous solution of ethylene glycol with excellent protection against aluminum corrosion, whereas, vinyltrimethoxysilane alone was found to contribute to the solution's corrosive effect (see Table II of U.S. Pat. No. 4,514,315).
It is an aspect of this invention to provide an alcohol-based composition inhibited against aluminum corrosion, particularly, aluminum cavitation erosion corrosion.